- Move documentation of libcurl environment variables used only in debug
builds from libcurl-env into a separate document libcurl-env-dbg.
- Document more debug environment variables.
Previously undocumented or missing a description:
CURL_ALTSVC_HTTP, CURL_DBG_SOCK_WBLOCK, CURL_DBG_SOCK_WPARTIAL,
CURL_DBG_QUIC_WBLOCK, CURL_DEBUG, CURL_DEBUG_SIZE, CURL_GETHOSTNAME,
CURL_HSTS_HTTP, CURL_FORCETIME, CURL_SMALLREQSEND, CURL_SMALLSENDS,
CURL_TIME.
Closes https://github.com/curl/curl/pull/11811
